DE3616334A1 - METHOD FOR DAMPING AT LEAST ONE ELECTRICAL HARMONOMY TO THE NETWORK FREQUENCY IN A MULTI-PHASE AC ELECTRIC NETWORK - Google Patents

Description

44/86

5/13/86

Method for damping at least one electrical Harmonics to the mains frequency in one

multi-phase alternating current network

The invention is based on a method for damping at least one electrical harmonic to the mains frequency in a multi-phase alternation Ist romnetz according to the preamble of claim 1.

\ i ι 5 With this generic term, the invention refers to a prior art method for damping at least one electrical harmonic to the network frequency in a polyphase AC network, as described by PV Goosen et al., FC / TCR Type Static Compensators in ESCOM's 132 kV Network, International Conference on Large High Voltage Electric Systems, August 29th-September 6th, 1984 in Paris, Cigre Paper No. 38-09, pp. 1-9, 1984. There, suction circuits or air throttles for static BI ind power compensators are connected in a delta connection, each in series with alternating current switches, which have anti-parallel thyristors, via a saturable 35 MVA transformer to a 132 kV AC power supply. Device the transformer at high currents

3G1G334

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magnetically in saturation, this creates an undesirable one first harmonic to the network frequency in the power supply network. Especially the one through the second harmonic instability caused is attenuated by the it caused a direct current component in the alternating current of the B Iind power compensator recorded with special DC converters and with a slow Integra I controller is corrected. For each branch of the delta connection a separate voltage regulation is provided. Additional borrowed is a filter for the second harmonic in the Built-in power circuit.

The disadvantage is that for each branch of the delta connection there is a special control loop and an additional one Filters matched to harmonics are required.

The invention, as it is defined in claim 1, solves the problem of specifying a method for damping at least one electrical harmonic to the network frequency in a multiphase AC network, that is effective attenuation with simpler means possible.

One advantage of the invention is a reduction in the cost of damping undesired harmonics. A control loop with a single stabilization signal for all controllable impedance branches is sufficient, connected to the saturable transformer. There is no need to individually control each phase of the AC switch. The stabilizing effect will achieved solely by controlling the AC switch. An additional expensive, designed for high currents applied harmonic filter is not required.

According to an advantageous embodiment of the invention Normal AC current converters are sufficient to measure the currents, since practically only the currents of the second harmonic have to be recorded. Because the direct current component does not have to be measured, no expensive and complex high-precision direct current converters are necessary.

For the relevant state of the art, there is also on Schweikardt et al., Closed Loop Control of Static Var Sources (SVS) on EHV Transmission Lines, IEEE PES A 78 135-6, 1978, referenced from a current-voltage regulator for a three-phase ignition pulse generator is known which can be used in connection with the present invention.

The invention is described below on the basis of exemplary embodiments. Show it:

1 shows a block diagram of a typical reactive power compensator connected to a three-phase network, which is connected to a three-phase network via a reactive power transformer in which harmonics to be damped can occur

is,

Fig. 2 shows a first embodiment of a regulator circuit for compensating harmonics in Connection to a blind power compensator according to Fig. 1,

3 shows a block diagram of a reactive power meter the regulator circuit according to FIG. 2,

36 Ί 6334

4 shows a second exemplary embodiment of a regulator circuit to compensate for harmonics, with active and reactive power as the measured variable are recorded and to a network-frequency reference value are related,

5 shows a third exemplary embodiment of a regulator circuit for compensating harmonics, in which active and reactive power are recorded as measured variables and are related to the first harmonic ^{for the} mains frequency as a reference variable,

6 is a block diagram of a three-phase / two-phase coordinate converter according to FIGS. 4 and 5 and

7 is a block diagram of a two-phase / three-phase coordinate converter according to FIG. 5.

In Fig. 1, 1 denotes a rectifier which Via a direct current intermediate circuit with an intermediate circuit choke 2 with an inverter 3 to a high-voltage DC direct current transmission system (HGO) is connected. The DC link voltage is 315 kV. The DC link reactor is for an output of 1 GW measured. The inverter 3 feeds via an HVDC transformer 4 a three-phase network 15 with an alternating voltage of 120 kV. The three-phase network 15 is via a Stepping down transformer 5 with another three-phase Power supply network, which has a network impedance of 6, a 50 Hz exchange I voltage of 765 kV and a mains voltage source 7 has connected. The three-phase network 15 is also via a magnetically saturable reactive power transformer 8, the secondary side AC voltage of which is 12 kV to one for a reactive power of 2 - 120 MVA

designed air throttle 9 and one for a reactive power Capacitor bank designed for 2 · 150 MVA or connected to a real power capacitor 10. Air throttle 9 and reactive power capacitor 10 are over AC power controllers or switches connected in series 12 or 13, which have antiparal le Ie thyristors, controllable. The controllable air throttle 9 is provided with two further controllable air throttles (not shown) the other two voltage phases are connected in a triangle, which is indicated by a triangle marked 14 is. The controllable inductive power capacitor is in the same way 10 connected in delta. Furthermore, the three-phase network via a Fi lter capacitor 11, which is for a reactive power of 300 MVA is rated, grounded.

Such a system, consisting of an alternating current switch 12, air throttle 9, AC switch 13, capacitor

10, reactive power transformer 8, filter capacitor

11, HVDC transformer 4, HGt) 1-3, step-down transformer 5, line impedance 6 and line voltage source 7, can instabiI and oscillate with the first harmonic (100 Hz) to the mains frequency of 50 Hz if the mains gain is large enough for the first harmonic, i.e. if the impedance is at the termination point of the reactive power transformer 8 is large at the first harmonic, and when the AC switch 12 is between 90 ° and 180 ° is controlled. The instability occurs even when related to the AC line voltage equidistant ignition pulses to the AC switch 12 can be submitted.

The second harmonic corresponding to the first harmonic Instability is a closed, self-exciting sphere. Take for a better understanding

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we assume that the mains voltage in the connection point of the BLind Power transformer 8 a small voltage with the second harmonic of the network frequency is superimposed. This causes a direct current component in the alternating current SWITCH 12. The G light current component generates an equal Flux component in the iron core of the reactive power transformer 8, so that its magnetizing current becomes asymmetrical and even harmonics, in particular also contains the second harmonic. This second har Monic current sees a large impedance at the connection point of the reactive power transformer 8 and generated a second harmonic voltage at this impedance. Thus the sphere of activity for the second is harmonic Instability closed.

Fig. 2 shows a stabilization circuit for the damping of harmonics, which supplement the already known current-voltage or reactive power regulation can be built in and stable operation of the B reactive power compensator allows. In all figures the same parts are provided with the same reference numerals.

The mains voltage U .. of 120 kV / 50 Hz of the three-phase network 15 is connected via a current transformer 17 to the star-connected primary winding which is earthed at the star point of the B lind power transf ormator 8. i "denotes the Compensator current and a compensator current signal proportional to this at the output of the current transformer 17 Secondary winding of the reactive power transformer 8 is via a current transformer 18 on the one hand with an alternating current switch 12 and on the other hand with an alternating current switch 13 connected. i_ denotes a total current

o U

through the two AC switches 12 and 13 and a this proportional total current signal at the output of the Lers river wall 18.

r - 11/86

The AC switch 12, on the other hand, is via a Current transformer 19 with the air throttle 9 in series and with a further two controlled air throttles, not shown of the other two voltage phases connected in delta. The AC switch 13 is via a Current converter 20 with the reactive power capacitor 10 in series and with another two, not shown, controlled Reactive power capacitors of the other two Voltage phases connected in delta. The two AC switches 12 and 13 receive their control signals from a current-voltage regulator 22 via an adder 23 and via a three-phase ignition pulse generator 24 connected to its output, as e.g. the above IEEE publication A 78 135-6 are known.

The current-voltage regulator 22 supplies a single control signal S23 to the ignition pulse generator 24 via the adder 23, depending on the compensator current signal i "and on a voltage _{signal U proportional to the mains voltage U n} . The voltage signal U can be tapped off at the secondary winding of the voltage converter 16. On the primary side, the voltage converter 16 is connected to the three-phase network 15.

The compensator current signal i "is the" + "input and

IN

the sum current signal I i_ the "-" input of an adder

o U

gtiedes 21 supplied. The adder is on the output side 21 with a current signal input of the closer in connection with FIG. 3 described reactive power meter 25 connected. A voltage signal input of the reactive power meter 25 is the voltage signal U from the output of the Voltage converter 16 supplied, which at the same time as

-JS- 1 ^ / 86

Frequency reference size serves. At output 47 the BI power meter 25 a reactive power signal Q as DC voltage value, the possible harmonics of the frequencies (2n ~ 1) f are superimposed, η integer £ 1, f = mains frequency = 50 Hz. Since the reference frequency for the BLiηdleistungsmesser 25 is 50 Hz appears the first harmonic of 100 Hz relative to the reference frequency f with a frequency of 50 Hz.

The output 47 of the blind power meter is with a Band pass filter 26 that allows 50 Hz oscillations to pass through, furthermore with a band pass filter 26 'that oscillates 150 Hz lets through, and with one or possibly more bandpass filters 26 ", the oscillations of the frequencies (2n-1) ■ pass f, η ä 3, connected. These band pass filters 26, 26 'and 26 "are on the output side, respectively via known +90 phase shifter or stabilization filter with also customary, two-sided Limiters 28 connected. These limiters 28 are on the output side each with a "+" input of the adding song 23 connected.

Instead of the magnetizing current i - i of the reactive power transformer 8 at the output of the adder 21 can be the current signal input of the reactive power meter 25 the current output signal of the current transformer 19 via the signal line 29 shown in dashed lines is supplied be.

The stabilization circle consists of the acquisition of the signal to be stabilized (magnetizing current i "-i '

N O U

or current through the air throttle 9), the conversion of the three-phase signal into a single signal (U, i / Q transformation), at least one bandpass filter that supports the

X- 44/36

(which) filters out the stabilization signature (s), at least a phase shifter and an adder, which (the) Stabilization signal (s) to the output signal of the normal Current-voltage regulator 22 added.

If only the second harmonic is to be attenuated, the band pass filters 26 'and 26 "with subsequent 90 ° phase shifts can be used
let be.

90 phase shifters and bilateral limiters

3 shows a block diagram of a BI ind power meter 25. i, i_, i_ denote input-side phase currents i gna le which are supplied by the output of the adder 21 or by three current converters 19, only one current converter 19 being shown in FIG. L) _D , U-, U_ denote input-side phase voltage signals that are supplied by the output of voltage converter 16. Hit 30 - 39 are coefficient generators with the coefficients specified in the blocks, with 40 - 43 Addierg songs with "+" inputs, with 44 and 45 multipliers and with 46 an adder, which is connected to the output of the via a "-" input Multiplier 44 and connected to the output of multiplier 45 via a "+" input. The desired reactive power signal Q is obtained at output 47, the G light voltage value of which is superimposed by a 50 Hz oscillation if the mains voltage has a second harmonic of 100 Hz.

In the embodiment of the invention according to FIG. 4 the B reactive power compensator instructs four per phase the secondary windings of the reactive power transformer 8 connected AC switches 51 - 54 with it Impedances L1, C1, C2, L2 connected in series via current transformers 55 - 58, where L1 and L2 are air chokes or inductances and C1, C2 capacitor banks

or capacitors. ALL four impedances one Three-phase phases are each with the four impedances of the two other three-phase phases connected in delta connection (not shown). The current signals at the output of the

Current transformers 55 - 58 are with i ' _Li /

_Li / ^ d '^ C2

net and "+" inputs of an adder 62 supplied, which is connected on the output side to a "-" input of an adder 63.

The current-voltage regulator 22 is on the input side with the Outputs of the voltage and current converters 16 and 17 and on the output side via a limiter 49 with adjustable unilateral limit value connected to a "+" input of the adder 23. Its only output sign L S23 controls the three-phase ignition pulse generator 24, the control pulses to the AC voltage switch 51 -deliver.

The compensator current signal i from the output of the current converter 17 is a “+” input of the adder 63

fed. Another "-" input of the adder 63 is connected to the secondary side via an integrator 48 Output of the voltage converter 16 connected. The integrator 48 supplies a magnetizing current signal from the reactive power transformer 8 on the output side

¹ M = Γ J " ^U N ^dt '

where L is a constant that corresponds to the main inductance of the reactive power transformer 8 corresponds. With i becomes the fundamental component of the magnetizing current recorded, not the proportion of any magnetic saturation peaks that may be present.

The output signal of the adder 63 thus delivers

the magnetic saturation component of the current, which as a result of current harmonics can occur and to whose attenuation is evaluated. The adder 63 is on the output side with the input 64 of a closer connection with Fig. 6 described three-phase / two-phase coordinate converter 65 connected.

From a reference frequency signal control set 117 are further inputs 68 and 69 of the three-phase / two-phase coordinate converter 65 line frequency and 90 phase shifted reference frequency signals relative to each other sin ü) t or cos ωί supplied, ω = 2πί = angular frequency, t = time. At the outputs 66 and 67 of the three-phase / two-phase coordinate converter 65 are an active power signal d that is fed to the input of a bandpass filter 70 leads is, and a reactive power signal q that the input a band pass filter 71 is supplied, can be tapped. The two band pass filters 70 and 71 allow 50 Hz oscillations happen so that their output signals χ and y are characteristic of the amplitudes of the active and reactive power components of the second harmonic of 100 Hz. Relating to the reference frequency of 50 Hz in three-phase / Two-phase coordinate converter 65 appears in the Current input signals at input 64 contained second Harmonics of 100 Hz at outputs 66 and 67 with a frequency of 100 Hz - 50 Hz = 50 Hz. The signals χ and y are set using a coefficient transmitter or setting potentiometer 72 or 73 "+" inputs of an adder 74, added there and then to the "+" input another adder 60 is supplied. A "-" input the adder 60 is supplied with a setpoint value 59 = 0. On the output side, the adder 60 is via a +90 phase shifter 27 or via a stabilization filter for the second harmonic and then via a bilateral limiter 28 with a "+" input

of the adder 23 connected. The two coefficient generators 72 and 73 are initially set to the value or factor "1" is set and then increased in value as long as until the harmonics are compensated.

At the same time, the signals χ and y are fed to an absolute value generator 75 in which the amplitudes of these signals squared and the square root is taken from the square. The starting side is the amount generator 75 via a coefficient generator 76 and via a timer 50 connected with a predefinable time delay to an input of the limiter 49, where the output signal of the Timing element 75 is used to set the limit value of limiter 49. Furthermore, the absolute value generator 75 is on the output side via another coefficient generator 77 and via a timing element 61 with a predefinable delay connected to an input of the two-sided limiter 28, where the output signal of the timing element 61 is used to set the two limit values of the limiter 28. The components labeled 65-77 are one Harmonic evaluation circuit indicated by dashed lines 78 summarized.

According to this differential current method, in which the sum the secondary currents and also the magnetizing current can be subtracted from the primary current Correct or prevent transformer saturation well. The individual currents are trimmed in such a way that the resulting current zero comes out in the unsaturation fa 11.

Instead of the above-mentioned differential current method, a summation current method can be used in which one Adder 63 'only the choke current signals i. .. and i _ the current transformers 55 and 58 and / or an adder 63 "

only the capacitor current signals i . and i _ the current transformers 56 and 57 are supplied as input signals containing harmonics. The adders 63 'and 63 "are connected on the output side to harmonic evaluation circuits 79 and 80, respectively, which are constructed in the same way as the above harmonic circuit 78. You can also only supply the compensator current i., Directly to the three-phase input of the three-phase / two-phase coordinate converter 65 to a harmonics evaluation unit 81, which has the same structure as the harmonics evaluation unit 78. The coefficient generators 76 of the harmonics evaluation units 79-81 are each connected on the output side to a "+" input of an adder 84, which is connected on the output side to the input of the timer 50 is the coefficient encoder 77 of the OberschwingungsauswertschaItungen. 79 - 81 on the output side in each case with a "+" - connected input of an adder 85, which is on the output side to the input of the timing element 61 in connection the adders 74 of the OberschwingungsauswertschaItungen. 79 - 81 on the output side in each case with a "+ "Input of an adder 86, which is connected on the output side to the" + "input of the adder 60.

The input-side limitation in limiter 49 is used the creation of a setting reserve for the control of the thyristors of the AC switches 51 - 54. The setting reserve is greater, the greater the amplitudes of the second harmonic; but it does not disappear when the second harmonic does not occur. It is important that as little reserve as possible is used so as much capacitive reactive power as possible is available stands.

The two-sided limitation in the limiter 28 as a function on the size of the occurring second harmonic serves to ensure that the normal regulation via the current-voltage regulator 22 is not impaired too much can be.

The reference frequency signal control set 117 has a three-phase / two-phase coordinate converter 87, the three-phase input of which is supplied with the voltage signal U from the output of the voltage converter 16 on the secondary side, the reference signal inputs of which are the reference frequency signals sin (ot and cos ωί from outputs 92 and 93 of a sine-cosine) -Generator 91 are fed and its two-phase outputs are connected to signal inputs of a proportional-integral or PI controller 88. On the output side, the PI controller 88 is connected to a "+" input of an adder 89, the output side of which is connected to a control input of the The sine-cosine generator 91 is connected to a second “+” input of the adder 89, a frequency setpoint value 90, corresponding to the network frequency f of 50 Hz, is fed.

Fig. 5 shows a harmonic stabilization circuit, which differs from that shown in FIG. 4 essentially only with regard to another harmonic evaluation circuit 115 and another reference frequency signal control set 116 differs. Hence the following is essentially only illustrated and mentioned what is different.

The frequency reference signal for the three-phase / two-phase transform has the frequency of the second harmonic and not that of the mains frequency f as with the Harmonic stabilization circuit according to Fig.

A three-phase / two-phase coordinate converter 98 of the harmonic stabilization circuit 115 receives the harmonics-containing compensator current i _K on the input side as well as reference frequencies i gna le sin 2iot and cos 2ωί from signal outputs 96 and 97 of a three-phase / two-phase coordinate converter 95 of the reference frequency signal. Tax rate 116 supplied. The active power and reactive power output of the three-phase / two-phase coordinate converter 98 are each directly connected to the "+" input of an adder 101 and 102, respectively (the low-pass filters 99 and 100 shown in dashed lines can be omitted). At "-" inputs of the adders 101 and 102, setpoint signals 103 and 104 with the setpoint zero are carried. On the output side, the two adders 101 and 102 are connected to the two-phase inputs of a two-phase / three-phase coordinate converter 107 via PI controllers 105 and 106. Reference frequency signal inputs of the two-phase / three-phase coordinate converter 107 are connected to the outputs 92 and 93 of a sine-cosine generator 91 of the reference frequency signal control set 116, which sine-cosine generator 91 supplies line-frequency signals sin cot and cos u) t. The three outputs of the two-phase / three-phase coordinate converter 107 are each connected to a “+” input of an adder 111 via a coefficient generator 108 or 109 or 110 for weighting, the output side being connected to a “+” input of the adder 86 is. The adder 86 is connected on the output side directly to the control signal input of the two-sided limiter 28, without the interposition of the adder 60 and the 90 phase shifter 27 according to FIG. 4. The output signal of the limiter 28 is fed back to the adder 23, see Output signals χ and y of the PI controllers 105 and 106

- YH, -

are also fed to an amount generator 112. Whose Output signal is on the one hand via a coefficient generator 113 a "+" input of the adding song 84 and on the other hand via a coefficient generator 114 a "+" Input of the adder song 85 supplied. The adding song 84 is on the output side via the timer 50 connected to the limiter 49, not shown in FIG. On the output side, the adder 85 is connected to the limiter 61 via the timing element 61.

In addition or as an alternative to the harmonic evaluation circuit 115, identical harmonic evaluation circuits can be provided which receive the output signals of the adders 63 ¹ and 63 "according to FIG 86. The output signal of the adder 63 according to FIG. 4 is preferably fed to the harmonic evaluation circuit 115 instead of the compensator current i ", the adders 84, S5 and 86 being omitted.

The reference frequency signal control record 116 according to FIG. 5 has the same structure with regard to the components 87-91 as the reference frequency signal control set 117 according to FIG Fig. 4. The outputs 92 and 93 of the sine-cosine generator 91 are via a two-phase / three-phase coordinate converter 94 with the three-phase / two-phase coordinate converter 95 connected, which supplies the sin 2ωί and cos 2ü) t signal at its outputs 96 and 97 and its Frequency reference signal inputs to outputs 92 and 93 are connected.

Instead of the adders 101 and 102 and the subsequent

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send PI controllers 105 and 106 of the harmonic evaluation circuit 115 can also use low-pass filters 99 or 100 be provided to block the frequencies above 10 Hz, there the second harmonic here as a DC voltage signal accrues. At the low-pass filters 99 and 100 are on the output side the signals χ and y can be tapped.

A three-phase / two-phase coordinate converter should now be based on FIG (65, 87, 95, 98), the three values R, S, T of a three-phase system in corresponding Values of a right-angled d, q coordinate system transformed. The angle between the two Coordinate systems is denoted by ε; he transforms the R, S, T values in a right-angled α, ß coordinate system. In this case, the α vector coincides with the R vector. The transformation equations Ring:

α = R,

β = (1 / YT) * (ST),
d = a · cos ε + β · si η ε, q = -α ■ sin ε + β ■ cos ε.

7 is a two-phase / three-phase coordinate converter (94, 107) explains the two values of a right-angled d, q coordinate system in three vectors transformed into a three-phase coordinate system. ε denotes the angle between the two coordinate systems. The rectangular d, q coordinates become by rotating through the angle ε into right-angled α-, transformed into β coordinates. The transformation equations ring:

Vg- 44/86

α = d ■ cos e - q ■ sin e, ß = d · sin ε + q -cose, R = α,

S = -0.5 ■ α + 0.5 l / T ■ β, T = -0.5 a - 0.5 TfT B.

The shades according to FIGS. 4 and 5 are for one Detection and attenuation of the second harmonic designed. It is understood that in a manner similar to that explained in connection with FIG. 2, others as well Harmonics, if necessary additionally, recorded and can be steamed. Additional harmonic evaluation circuits must then be provided, which are tuned to these harmonics.

The mains frequency f can of course be used instead of 50 Hz also e.g. be 60 Hz.

Instead of AC switches 12, 13 and 51-54 with two anti-parallel thyristors, several such alternating current switches can also be connected in series.

In the circuits according to FIGS. 4 and 5, the active power component d and / or the reactive power component q can be weighted, added or subtracted, before going to the second harmonic stabilization filter are supplied, the output signal of which is directly namely three-phase, not phase-individually, on the Ignition pulse generator 24 acts.

In the circuit according to FIG. 5, two of the three Coefficient generator 108-110 have the coefficient zero. It is essential that only one control signal S23 is used to control all three phases. Preferential

. £ ⁰ J ° ^ö0 ^ 4H / 86

The Signa L is evaluated and generated in a wise manner Control signal S23 in digital form by means of a fast Microprocessor. This allows AC grids with existing, conventional B I ind power compensators can be easily supplemented and attenuated with regard to disruptive harmonics.

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Claims (8)

Claims 1. Method for damping at least one electrical Harmonic to the line frequency in a polyphase AC network, a) to the at least one impedance (9, 1O _x L1, Li, C1, C2) via a magnetically saturable transformer (8) and at least one gate-controlled AC switch (12, 13, 51-54) connected is, b) depending on an equidistant control signal a current-voltage regulator (22) controlled will, c) where depending on the current (i_, Vi 'V?' i _c1 , i _c2 ) a stabilization signal is generated by at least one impedance (9, 10, L1, L2, C1, C2), d) after a phase shift of + 90 ° the output signal of the current-voltage regulator (22) in A negative feedback of the harmonic is superimposed, characterized, e) that as a function of the input voltage (U _n ) of the transformer (8) and as a function of at least the current through an impedance (9, 10; L1, L2, C1, C2) at least one electrical power signal (Q; ρ, q) is generated with an active and / or reactive power component (p, q), f) that each power signal has at least one frequency filtering for each electrical harmonic to be compensated and g) then subjected to the phase shift by +90 before the equidistant output - & r - 44/86 signal of the voltage regulator is superimposed on a control signal (S23) for the AC switches, 2. The method according to claim 1, characterized in that a) that each filtered, phase-shifted stabilization signal for phase limit values exceeding a specifiable lower and upper phase limit value monitored and, in the event of limit values being exceeded, to the lower or upper limit value is limited, b) where the phase limit values are dependent on the amplitude of the harmonics to be damped are that with a larger amplitude a stronger limitation results, c) that each stabilization signal so limited to the equidistant output signal of the current-voltage regulator (22) is added, d) in particular that any stabilization signal before the phase shift is weighted (α) in such a way that it is in the non-saturation fa 11 of the transformer (8) assumes the value zero, and that it is delayed in time by a predeterminable first period of time before it becomes the equidistant output signal of the current-voltage regulator added will. 3. The method according to claim 1 or 2, characterized in that a) that the current signal for forming the at least one electrical power signal as a function of the primary input current (i ' _K ) of the transformer (8) or 5616334 b) as a function of the sum of the inductive currents (i,., i.J of the impedance (L1, L2) or c) depending on the sum of the capacitive currents (i _c1 v ¹ T? ^ ^the impedance (C1, C2) is formed. 4. The method according to any one of claims 1 to 3, characterized marked chnet, a) that the current signal for forming the at least one electrical power signal is the sum of the inductive and capacitive currents (i_; i. <., i. ₂ , Vi ' ⁷ c2 ^ ^{of at} least one impedance (9, 10; L1, L2, C1, C2) is subtracted from the primary-side input current Ci _1. ) Of the transformer (8), b) in particular that of the differential current formed in this way one derived by integration from the input voltage (U) of the transformer (8) Transformer magnetizing current (i) is subtracted. 5. The method according to any one of claims 1 to 4, characterized in that i chnet, a) that a measurement of the harmonics as active and reactive power components (d, q) by means of a three-phase / two-phase coordinate transformation from the input signals containing the harmonics (U, i; i _K , i _Su , i _M ; i _u , i, _ ₂ ; i ^, i _c2 ; i ") based on a line frequency reference frequency quenz (sin ü) t, cos cot) takes place, b) that each power component has at least one Bandpass filtering (2.6, 26 ', 26 ", 70, 71) subjected will, c) wherein each band pass filter is on one of the frequencies (2n-1) ■ f, η integer ä 1, f = Net ζfrequency, is matched. d) that the two filter output signals (χ, y) of the band pass filter tuned to a specific frequency (70, 71) are added as the square of the two power components, e) that the square root is taken from the sum of squares thus formed, f) that depending on the square root signal formed in this way, the equidistant output signal of the Current-voltage regulator (22) limited in such a way on one side (49) means that the setting reserve of the current-voltage regulator increases the larger the value is the square root, corresponding to a larger amplitude of the harmonic to be damped, g) in particular that the square root signal is weighted (α) and a time delayed by a predeterminable second period of time before the equidistant Output signal of the current-voltage regulator (22) limited. 6. The method according to any one of claims 3 to 5, characterized in that a) that the alternating current network (15) is a three-phase Three-phase network is and every alternating current switch (12, 13; 51 - 54) is controlled in three phases and b) that at least one bandpass filter on the line frequency (f) is matched. 7. The method according to any one of claims 1 to 4, characterized in that a) that the measurement of the harmonics as an and reactive power component by means of a three-phase / two-phase coordinate transformation (98) from the input signals containing the harmonics ^ _ 44/86 nalen (U, i; i ^ i _{$ u} , 1 _H ; \ ^, i ^; i ^, i ^; ^) takes place, based on a reference signal with the frequency of the second harmonic to the mains frequency, b) that each service component is subsequently one Low-pass filtering or proportional-integral control is subjected c) that the two filter output signals (χ, y) for the two power components are added as the square, d) that from the thus formed square sum the square root is pulled e) that depending on the square root signa formed in this way I is the equidistant output signal of the current-voltage regulator (22) is limited on one side (49) in such a way that the adjustment reserve of the current-voltage regulator The larger the value of the square root, the larger it becomes, corresponding to one greater amplitude of the harmonic to be damped, f) in particular that the square root signal is weighted (α) and is delayed in time by a predeterminable second period of time before the equidistant Output signal of the current-voltage regulator (22) limited. 8. The method according to claim 7, characterized in that a) that the alternating current network (15) is a three-phase Three-phase network is and every alternating current switch (12, 13; 51 - 54) is controlled in three phases and b) that the output signal of each low-pass filtering or proportional-integral control of a two-phase / three-phase coordinate transformation ion loading moved to a line frequency reference frequency egg is thrown before it is shifted 90 ° in phase